Japanese Unexamined Patent Application Publication No. 2012-226392 (paragraphs [0021] to [0023]) provides a drive assistance system that executes two types of travel assistance, in particular, lane keep assistance (also referred to as lane keep control) and lane change assistance (also referred to as lane change control). The drive assistance system provides the lane change assistance in response to an operation (a winker operation) with a direction indicator. If the direction indicator is operated during the lane keep assistance, it is checked whether or not the other vehicle is present at the front and rear lateral side, if the other vehicle is not present, the lane to be kept is changed from the current lane to a lane in a change direction, and the lane keep assistance is continued.
Japanese Unexamined Patent Application Publication No. 2012-226392 describes restriction of the lane change control if the other vehicle is present at the rear lateral side when the direction indicator is operated during the lane keep control; however, does not describe the lane keep control after the situation. In general, a vehicle of related art that executes only the vehicle keep control as travel assistance is configured to cancel the lane keep control in response to an operation with a steering wheel or the direction indicator. As compared with the vehicle of related art, the configuration described in Japanese Unexamined Patent Application Publication No. 2012-226392 invalidates the lane change control and cancels the lane keep control if the other vehicle is present at the rear lateral side when the direction indicator is operated. That is, even when a driver intends to continue the lane keep control after changing the lane, the lane keep control may be canceled contrarily to the intention of the driver.